1. Field of Invention
The management of spinal deformities has undergone major changes in the past decade, especially with the introduction of the multi-hooked segmental rigid fixation devices that have entered the market. This invention relates to segmental spinal instrumentation, specifically metal spinal hooks and rods used for the correction of spinal deformities such as idiopathic scoliosis.
2.Description of Prior Art
Several spinal implant systems currently exist on the market today. Many of these systems demonstrate deficiencies related to the manner of connecting the rod to the spinal hooks used in the spinal fixation system. The main advantage of the present spinal system is the ease in reducing the spinal rod to the hooks, thus saving time in the operating theater. Some problems with prior systems are found when inserting the hook and rod constructs. There are many parts and many steps in the assembly of those parts. The numerous parts and steps leads to additional time spent in the operating theater leading to increased morbidity for the patient and increased operating expense. The present invention both simplifies and reduces the number of steps effectively lessening the time spent in the operating theater, in that the spinal hooks and tool used during the operation have been redesigned. Specifically, the hooks and tool used for reducing the rod to the hook for placement of the set screw to secure the rod in place have been redesigned. Previous systems illustrate elaborate methods for reduction of the rod to the hook when the distance is greater than approximately 0.5 inch. For example, one spinal implant system teaches the surgeon he should use three tools for the reduction when he is unable to reduce the rod because it remains at a distance too great to use a screwdriver alone. First, the hook is secured with a clamp encompassing the hook and rod; this also obscures the view of where the set screw is placed. A second device is attached to the side of the first device and is braced against the rod. A third device, identical to the second device, is attached to the opposite side of the first device and is braced against the rod. Using a screw method, the second and third devices are turned clockwise, advancing a screw mechanism which pushes the rod down to the secured hook. After the rod is seated the set screw is placed on the hook through the top of the first device that is hollowed out for set screw placement. Finally, the second and third devices are unscrewed and removed, and the first device is unclamped and removed after which the next hook may be reduced.
Other spinal hook and rod systems have the same problem as illustrated above with more complicated methods of securing the rod to the hook.
Specifically, another spinal hook and rod system requires additional steps after a similar reduction of the rod to the hook. To place the securing set screw, another device is required to position an end cap, which contains the set screw, partially on the hook. This first device is then removed and a second device is placed to push the end cap fully on the hook. This device is then removed and finally the set screw may be tightened after the end cap containing the set screw is correctly positioned. This clearly demonstrates difficulties encountered with this system and highlights the need for multiple instruments in the insertion and procurement of fixation of the rod and hooks.
Another different spinal system includes many instruments for the insertion of the device. Additionally, many extra steps are required to use these instruments. Specifically, to reduce the rod to the hook special rod-introduction pliers are used. The pliers must be pre-loaded with a collar. These pliers are then placed over a protruding pin which is attached to the hook. The pliers then engage the rod and align the hook and rod. Then another tool is used to release the collar which temporarily retains the rod. After the pliers are removed a nut is placed to permanently secure the collar to the hook.
Other spinal implant systems currently existing on the market today exhibit the same, similar or greater disadvantages including but not limited to those described above. Additional disadvantages of the existing spinal hook and rod systems are realized by recognizing the need to remove and replace the hooks and rods in surgical patients. Many of the steps of placement must be reversed to remove or reset the rods and hooks, adding time to the procedure. Further, The manufacturing of the hooks with more parts generally presents difficulties with the complex machining. Additionally, the manufacturing of multiple, complex hooks and additional tools for insertion of the hooks requires extra machinery for high volume production.